As urban centers increase in size, and traffic congestion becomes more common, the need for accurate and up-to-date traffic information also increases. Traffic surveillance relies primarily on traffic sensors, such as inductive loop traffic sensors that are installed under the pavement. Alternatively, video sensors may also be used to obtain traffic information.
Residing underground, inductive loop sensors are expensive to install, replace and repair because of the associated roadwork required. Moreover, such roadwork also causes traffic disruptions. Video sensors, on the other hand, are cheaper, but have other drawbacks, such as an inability to operate in the dark or in weather that impairs visibility, such as fog or snow.
To overcome these drawbacks, radar sensors have been employed to obtain traffic information. Radar sensors typically transmit low-power microwave signals at the traffic, and detect vehicles based on the reflected signals. Radar sensors are generally cheaper than inductive loop traffic sensors, and, unlike video sensors, operate well in the dark and in a wide range of weather conditions.
Some processing of the reflected signals takes place in the radar sensor itself, and then this information is typically communicated to an external traffic management system. For example, some prior sensors include a single DSP processor that performs all of the computational functions required by the traffic sensor. Alternatively, in other prior radar sensors, the processing functions of the radar sensor are divided between a DSP processor which processes a stream of electrical signals from a receiving antenna of the radar sensor, and a microcomputer for processing the stream of digital signals received from the DSP. In this processor architecture according to the prior art, the DSP would perform raw signal processing on the reflected signals received from the receiving antenna, while the microcomputer would determine if a vehicle was present.